Existing known systems for checking the integrity of elongate tools, like drills or centers or boring bars, stored in the machine storage magazine and substantially arranged along parallel axial directions, include contact detecting systems. More particularly, an embodiment foresees the use of a mechanical feeler with a flat surface that is abutted, by the action of a movable slide, against the tool to be checked in the axial direction. Upon contact occurring between feeler and tool, a signal is provided for controlling the detection of the position of the slide, enabling to check the length and thus the integrity of the tool. The flat surface of the feeler—transversally arranged with respect to the feed direction of the slide—in general has a not negligible extension (for example, a few tenths of millimeters), for assuring contact with the end of the tool even in the case the latter is not perfectly aligned along its associated axial direction.
This condition is rather frequent, in consideration of the fact that each tool (more specifically, its associated toolholder) is coupled to a seat of the storage magazine with a not too accurate, slack coupling, conversely as to what occurs when the tool is coupled to the spindle in the course of the machining phase.
The use of contact detecting systems for checking purposes is critical in consideration of the possible damage that contact with the feeler can cause to the tools, especially in the case of tools with particular delicate coatings. There are known apparatuses and methods that utilize light beams for checking the dimensions or the presence, the arrangement and the possible breakages of tools.
U.S. Pat. No. 3,912,925 discloses, for example, a drilling machine in which the devices for checking the integrity of the tools utilize transversal light beams with limited thickness. The beams are substantially coplanar to the feed direction of the tools. The non-interruption of the light beam at a specific position on the tool is detected and notifies an anomalous condition of the tool. Devices as those disclosed in patent No. U.S. Pat. No. 3,912,925 are not suitable for checking tools arranged in the tool storage magazine, owing to the possible inclinations of the tools with respect to the axis due, as previously, to the inaccurate coupling between tool and associated seat.
Japanese patent application No. JP-A-9/300178 and its English abstract disclose the checking of a rotating elongate tool coupled to the spindle of the machine tool, in which the position of the end of the tool is checked by detecting, by means of a linear sensor, the partial interruption of a substantially plane beam or bundle of light. The presence of the linear sensor enables to obtain also information on other characteristics of the tool (diameter, length, type of tool), by processing signals indicative of the quantity of intercepted light.
The embodiment according to the former Japanese patent application is particularly expensive, especially in those cases when there is the need to simply check the integrity of the tool.